How to Enable SSL Encryption in Lion’s iCal Server
To enable SSL encryption with Lion’s iCal Server, you simply assign an encryption certificate to the iCal service. You can use the self-signed certificate that Lion Server’s setup process created (which users will have to manually accept) or a signed certificate from a certificate authority.
You can use the Server app to assign an SSL certificate to iCal server:
Make sure that you have turned on the iCal Server.
In the Server app, click the iCal icon.
Click the big switch to the On position.
In the Server app, under Hardware, select your server and click the Settings tab.
Click the Edit button next to SSL Certificate.
If your running services have different SSL settings (such as different certificates or some with No SSL assigned), you see a list of services and their SSL settings.
If all your services have the same setting, the dialog displays only the Certificate menu, with either the word None or the name of the certificate. If this is the case, click the menu and select Custom to arrive at the screen.